The present invention relates to a process of producing a water-soluble hemicellulose, in which the B fraction of hemicelluloses contained in rice bran, wheat bran or grain husk and having various kinds of physiological effect is extracted and separated from the bran or the husk, and to the use of water-soluble hemicellulose.
Cellulose, hemicelluloses, pectic substances, lignin, chitin, mucilages (galactomannan, glucomannan and the like), algal polysaccharides, chemically modified polysaccharides (chemically modified starch, carboxymethylcellulose and the like), etc. are designated as dietary fibers, and they are indigestible constituents which are contained in food and indigestible in human digestive enzymes. Recently, it is noted that the ingestion of these dietary fibers shows physiological effects. These dietary fibers are classified into water-soluble fibers and water-insoluble fibers.
It is reported that the water-soluble dietary fibers have the following advantages: 1) the fibers prevent the absorption of toxic substances or carcinogens present in the intestines and the fibers are excreted with these materials, 2) cholesterol, bile acids and heavy metals adhere to the fibers and these are excreted, and 3) the intestinal surroundings are improved by useful bacterias which are predominantly present in the intestinal micro flora. The insoluble fibers have the following advantages: 1) the fibers stimulate the motility of the large bowel and accelerate large bowel transit in spite of the slower transit time through the stomach and small intestine, and 2) the fecal water content and fecal weight are increased.
The B fraction of hemicelluloses which is a kind of water-soluble fibers has been studied because it has various kinds of physiological effect. A fractionation procedure of the hemicellulose, B fraction has been reported by Southgate, D. A. T. "The Chemistry of Dietary Fiber" in "Fiber in Human Nutrition", edited by Spiller, G. A. and Amen, R. J., pp31, Plenum Press, NY (1976), since then, several fractionation procedures of the hemicellulose B fraction have been reported (Japanese Patent Publication Numbers 59-1687, 59-1688 and 59-1689, Japanese Laid-Open Patent Publication Number 60-27365). However, the procedure of industrial mass production of hemicellulose B is yet unknown. As the reason, it is considered that each process cost much money and is time-consuming.
A food which is obtained by adding fibers is described in Japan Laid-Open Patent Application No. 58-187745. The food is obtained by adding fibers to processed food such as, for example, soy-bean paste, bean-curd, retort foods, pies or bread. The addition aims to obtain characteristics of resistance to age, prevention of water-staining, prevention of concretion, viscosity control, prevention of oil separation and the like. The addition does not aim to obtain food containing the hemicellulose B fraction for the main ingredients. The food contains only a little hemicellulose B fraction which has physiological useful effects. Accordingly, the physiological effect of the hemicellulose B fraction is not noticed in the above application.
In Japanese Laid-Open Patent Application No. 57-21324, it is described that hemicellulose which is extracted in alkaline solution from corn fibers inhibits hypercholesterolemia. However, the present invention is different from the above application, because the obtained hemicellulose in the present invention is separated and extracted from rice bran, wheat bran or grain husk which has effect in the most preferable conditions suitable for drinks and milk powder.
In Japanese Laid-Open Patent Application No. 63-165325, a kind of medicine for intestinal disorders which contains hemicellulose B fraction as an effective ingredient is disclosed. In the separation and extraction process, the removal of protein by using trichloroacetic acid and the purification by using ethanol precipitation are required, and the process is complicated.
In the U.S.A., milk powder in which fiber is mixed in the form of microcrystalline cellulose (MCC) for improving the property of is commercially available. However, since the MCC is a semi-synthesized product compound, its texture is bad. When the MCC was mixed with milk powder and dissolved in water, coagulation of colloids occurs. When it is added to drinks, the obtained drinks taste bad. Moreover, since the cellulose is a food fiber insoluble in water, it is impossible to expect the physiological effects which the above water-soluble food fiber have.
In Japanese Laid-Open Patent Application No. 61-24251, a low-caloric powder obtained by powdering the mixture of milk powder, beer yeast for food, saccharide which is not absorbed in the intestines and fibers is disclosed. The fibers described in the above invention are psylliun, pectin, guar gum and carrageenan. These fibers are slightly soluble in water and/or have high viscosity, so that when these fibers are added to milk powder, the treatment is troublesome and the obtained drinks containing the food fibers have bad texture.